Bobbin-thread case for sewing machines



Filed Jan. 2, 1937 Zlvwemtom Alfied R. Il bocl Patented Nov. 9, 1937 Alfred R. Wood, Bridgeport, Conn, assignor to The Singer Manufacturing Company, Elizabeth, N. 3., a corporation of New Jersey Application January 2, 1937, Serial No. 118,846

I 8 Claims.

This invention relates to stationary bobbinthread cases, of the type commonly associated in a sewing machine with a circularly moving loop-taker to hold the bobbin-thread mass for passage therearound of successive needle-thread loops seized by the loop-taker. A thread-case of the type in question is commonly provided with an upwardly extending rotation-restraining arm which is loosely received in a notch in a rotation-restraining bar or plate fixed to the frame of the sewing machine.

The bobbin-thread commonly leads from a bobbin, which is disposed within the thread-case, through a slot in the cylindrical wall of the thread-case and thence circumferentially of the thread-case under a flat tension spring the free end of which commonly terminates at the top side of the thread-case; the bobbin-thread leading upwardly from the free end of the tension spring to the work.

In sewing certain classes of work such, for example, as lock-stitch pyramid-purl button-holes of the type disclosed in United StatesPatent No. 1,021,399, of Mar. 26, 1912; the requirement of uniformity of action of the bobbin-thread -ten-' sion-device is exacting and variations in the bobbin-thread tension cannot be tolerated. It has been found that at high speeds of operation there is a tendency for the upwardly leading bobbin-thread to momentarily lift the free end of the tension spring off of the cylindrical wall of the thread-case and thus render it momentarily ineffective. This results in a lack of uniformity in the stitching.

The present invention has for an object to provide a cup-shaped stationary thread-case of the type having a bobbin-thread tension spring applied circumferentially to its external cylindrical wall, with means to prevent the upwardly running bobbin-thread from lifting the free end of the tension spring away from the thread-case.

With the above and other objects in View, as will hereinafter appear, the invention comprises the devices, combinations and arrangements of parts hereinafter set forth and illustrated in the accompanying drawing of a preferred embodiment of the invention, from which the several features of the invention and the advantages attained thereby will be readily understood by those skilled in the art.

Referring to the drawing, Fig. 1 is a. front elevation of a sewing machine shuttle embodying the invention. Fig. 2 is a top plan view of the bobbin thread-case carried by the shuttle. Fig.

3 is a section on the line 3-3, Fig. 2. Fig. 4 is a section on the line 4-4, Fig. 2. Fig. 5 is a section on the line 5-5, Fig. 2.

The shuttle body ;A, of the oscillatory type, hast-he usual needle-loop-taking beak I and semicircular bearing rib l centrally of which is the arbor 2 on which is journaled the central tubular element 3 of the cup-shaped thread-case body B carrying the bobbin 4 Wound with bobbinthread 5. The thread-case is formed as usual with the upwardly extending rotation-restraining arm 6 which, in practice, engages a notch in a rotation-restraining bar or plate (not shown) mounted on the frame .of the machine.

Applied circumferentially to the outer cylin drical wall of the thread-case body B is the arched bobbin-thread tension leaf-spring i, one end portion of which engages under the edge 8 and over the edge 9 of the aperture iii in the thread-case wall. The free .end portion of the tension-spring l bears upon the bobbin-thread 5 which leads outwardly from the bobbin 1 through the usual threading slot H and extends circumferentially of the thread-case under the tension-spring l. The thread-case body B is formed in the top side of its cylindrical wall with a circumferentially extending slot 12 and the free end portion of the tension-spring I, from under which the bobbin-thread issues, terminates substantially at one end of the slot l2, see Fig. 2. The pressure of the tension-spring I upon the bobbin-thread is regulated by the tension screw it in the usual manner.

Secured at one end by the screw I4 to the seat l5 in the thread-case body B at the base of the rotation-restraining arm 6 is the thread-guide H5 in the form. of a bar which extends in a directional normal to the direction of length of the tension-spring 1 across the slot I2 immediately adjacent the free end of the tensionspring. The thread-guide i6 is applied to the circumferential wall of the thread-case independently of the tension-spring l and is longer than the width of the free end portion of the tension-spring, so that the bobbin-thread leading from the threading slot ll may be directly drawn or passed under the free end of the threadguide [6 and into the thread-receiving notch ii in one edge thereof; the bobbin-thread leading upwardly from the notch I! to the work.

It will be clear that the thread-guide I 6 relieves the free end of the tension-spring of any lifting strains caused by jerks on the bobbinthread, and that the bobbin-thread will at all times be subjected to the uniform pressure of the tension-spring 1..

The bar [6, because of its thinness, does not interfere with the oscillatory movement of the shuttle body A, even though it is applied to the outer cylindrical wall of the thread-case. Further, it does not impede the threading up of the thread-case or ofier any obstruction to the drawing up of the needle-thread loops which are seized by the shuttle beak and distended for passage around the shuttle and thread-case carried thereby.

Having thus set forth the nature of the invention what I claim herein is:

1. A bobbin-thread case, for sewing machines, having a cylindrical cup-shaped body, a free ended tension leaf-spring applied circumferentially to the cylindrical wall of said body, and a thread-guide applied to the cylindrical wall of said body independently of said tension spring and disposed immediately adjacent the free end of the latter.

2. A bobbin-thread case, for sewing machines, having a cylindrical cup-shaped body, a free ended tension leaf-spring applied circumferentially to the cylindrical wall of said body, and a thread-guide applied to the cylindrical wall of said body independently of said tension spring and disposed immediately adjacent the free end of the latter, said thread-guide comprising a thin flat bar normal to the direction of length of said tension spring.

3. A bobbin-thread case, for sewing machines, having a cylindrical cup-shaped body, a free ended tension leaf-spring applied circumferentially to the cylindrical wall of said body, and a thread-guide applied to the cylindrical wall of said body independently of said tension spring and disposed immediately adjacent the free end of the latter, said thread-guide comprising a thin flat bar normal to the direction of length of said tension spring, said bar having a thread-receiving notch in one edge and being longer than the width of the free end-portion of said tension spring.

4. A bobbin-thread case, for sewing machines, having a cylindrical cup-shaped body formed with an opening in the cylindrical wall thereof, a tension leaf-spring applied circumierentially to the cylindrical wall of said body and having a yielding free end terminating adjacent said opening, and a thread-guide overlying said opening.

5. A bobbin-thread case, for sewing machines, having a cylindrical cup-shaped body formed with an opening in the cylindrical wall thereof, a tension leaf-spring applied circumferentially to the cylindrical wall of said body and having a yielding free end terminating adjacent said opening, and a thread-guide bar secured at one end only to said body and extending entirely across and beyond said opening.

6. A bobbin-thread case, for sewing machines, having a cylindrical cup-shaped body and a rotation-restraining arm projecting therefrom, said body having a slot in its circumferential wall, a thread-guide arm secured at one end only to said body at the base of said rotation restraining arm and extending across said slot, and a tension leafspring applied circumferentially to said body and having a free end terminating substantially at one end of said slot.

7. A bobbin-thread case, for sewing machines comprising a cylindrical cup-shaped body having in the cylindrical wall thereof a circumferentially extending slot, a tension leaf-spring applied circumferentially to said body and having a free end portion terminating substantially at one end of said slot, and a thread guide secured at one end to said body and crossing said slot.

8. A bobbin-case comprising a cylindrical cupshaped body having a single inclined threading slot cut into the cylindrical wall of said body from the rim thereof, a tension leaf-spring applied exteriorly to the cylindrical wall of said body and partially covering said threading slot, and a thread guide applied exteriorly to the cylindrical wall of said body immediately adjacent the free end of said tension spring, said thread guide being in the form of a bar which is secured at one end to said bobbin-case body and has a free end portion under which the thread leading from said threading slot may be directly drawn.

ALFRED R. WOOD. 

